Knix SuperPlus Leakproof No- Show High Rise Underwear
Skip unless Knix discloses waterproof coating chemicals.
Leakproof coatings commonly rely on PFAS-based water-repellent coating treatments, but Knix doesn't disclose coating chemistry or PFAS status. Third-party testing would help.
The better-graded swap
Lunapads
3-Pack BOOST Brief
100/100 safety
Same rubric that flunked this product. The swap earned Excellent.
Still want this one anyway? Check the price on Amazon. We’d swap it.
Material
Cotton/synthetic blend with proprietary waterproof/leak-resistant coating (unspecified)
Lab data
No public lab test
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What Knix SuperPlus Leakproof Rise Underwear is made of, ingredients and materials
Knix SuperPlus combines cotton and synthetic fibers with a proprietary waterproof/leak-resistant coating that the brand does not publicly identify by chemical name. This coating is the core functional element but also the primary source of concern, as synthetic waterproof finishes on textiles traditionally rely on fluorinated or silicone-based polymers. Cotton itself is low-risk; the blend ratio and coating durability under repeated washing determine safety exposure over product lifetime.
What’s concerning
Category baseline
The starting point for this type of product, before anything specific to this product is counted.
No PFAS disclosure
No public statement from the brand about PFAS in this product.
Waterproof / stain-resistant treatment
Water-repellent coating treatments have historically used PFAS.
Undisclosed waterproof coating chemistry (likely fluorinated or silicone polymer)
The proprietary coating is necessary for leak resistance but Knix has not publicly named the chemical type or stated whether it is PFAS-free. Historical industry practice suggests potential use of fluorinated water-repellents, though silicone alternatives exist. Degradation with washing and heat may increase skin contact over the product lifetime.
Coating degradation and microparticle shedding with repeated wash cycles
Synthetic waterproof coatings on textiles degrade gradually with laundering, especially in hot water or with mechanical stress. Fine particles or coating flakes may shed into wash water or remain on skin; long-term exposure safety is not well characterized for this emerging product category. Replacement every 6-12 months is recommended partly because coating efficacy decays.
What’s reassuring
Formaldehyde / VOCs
No specific findings on record for Knix period underwear. Low-level formaldehyde use in synthetic textiles is common for wrinkle resistance and dye permanence, but cotton-blend construction and non-obvious synthetic finish suggest likely minimal use. Lack of OEKO-TEX certification means no independent verification of formaldehyde limits.
Source, ATSDR ↗Heavy metals
Knix products are typically black or neutral colors, which may use carbon black or low-risk dyes, but no public testing or brand statement confirms exclusion of restricted azo dyes or metal salt dyes. No recalls or contamination reports exist for this product.
Source, FDA ↗Skin sensitization to coating residues or undisclosed polymers
No specific adverse-event reports are on record for Knix period underwear. However, the proprietary coating applied directly to skin-contact areas poses a theoretical risk if chemical residues remain after manufacturing or washing. Individuals with sensitive skin or polymer allergies should consider patch testing or requesting safety data from the brand.
How is this PFAS grade calculated?
The brand's record and disclosure
Knix has not publicly disclosed the chemical composition of its waterproof coating, which is unusual for a premium period-care brand in a market increasingly attentive to PFAS and chemical transparency. The brand has marketed sustainability and comfort but has not obtained third-party certifications (e.g., OEKO-TEX, GOTS) that would verify absence of restricted chemicals. No major safety recalls or contamination findings are on public record for this product line.
How it compares in its category
Period underwear is a newer category without standardized safety benchmarks. Knix competes with brands like Thinx, Aisle, and Modibodi, many of which also use proprietary coatings but sometimes claim PFAS-free or disclose alternatives (e.g., silicone-based without fluorine). Knix's silence on coating chemistry places it in a less transparent position than some competitors, though no public testing has confirmed higher PFAS levels than rivals.
If you buy it
Wash in cold water and avoid heat drying; tumble dry low or air dry to prevent coating degradation, which can increase leaching and reduces product lifespan. Replace every 6-12 months depending on wash frequency, as waterproof coatings degrade over time and efficacy declines before visible damage occurs. Do not bleach or use fabric softeners, which can compromise the coating. If you have concerns about synthetic coating exposure, contact Knix directly to request coating chemical disclosure before purchase.
What is not known about PFAS in this product?
- Basis
- Model estimate, 45% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- Knix has made a specific claim
Formulations change between production runs, so check the current label. How we grade.
What are the PFAS-free alternatives to Knix SuperPlus Leakproof No- Show High Rise Underwear?
- organic cotton, waterproof backing layer
- A third party reports verifying it as PFAS-free
- Coating degradation and microparticle shedding
2 hazards checked on this product, all on its full breakdown.
- organic cotton blend, water-resistant gusset
- The brand calls it PFAS-free, which we have not verified
- Microplastic shedding from water-resistant barrier
- Organic cotton, wood pulp fiber
- The brand calls it PFAS-free, which we have not verified
- Azo dyes and synthetic dyes
2 hazards checked on this product, all on its full breakdown.
More period underwear grades
How we score, every product runs through the same public 0-100 rubric based on materials, coatings, brand disclosure, lab findings, and recalls. See the full methodology → Spotted a mistake? Report an error.